1. Field of the Invention
The present invention relates to a process for producing optically active 2-halo-1-(substituted phenyl)ethanol and substituted styrene oxide and for heightening optical purity of 2-halo-1-(substituted phenyl)ethanol.
The optically active 2-halo-1-(substituted phenyl)ethanol produced according to the process of the present invention is useful as an optically active intermediate for medicines and agricultural chemicals. For example, it may be used for the production of optically active ketene S,S-acetals as disclosed in Japanese Patent Application Laid-open No. Sho 60-218387 (218387/1985). 2. Description of the Prior Art
Optically active styrene oxide may be produced with the aid of microorganisms as disclosed in Japanese Patent Application Laid-open No. Hei 4-218384 (218384/1992); it may also be produced from styrene by conversion into asymmetric diol as reported by K. B. Sharpless et al. [J.O.C.(1992), 57, 2768] However, these processes for asymmetric synthesis are not necessarily satisfactory from the standpoint of operating efficiency, yields, optical purity, and production cost.
There has long been a known process for converting a racemic alcohol into a phthalate ester and optically resolving it using an adequate resolving agent. [A. W. Ingersoll (1994), Org. React., vol. 2, 376] However, nothing is mentioned therein about the compound such as 2-halo-1-(substituted phenyl)ethanol, which has substituent groups in the benzene ring and alkyl chain. There is a literature which mentions that there exists no principle that can be applied, in resolution of diastereomers, to the selection of a resolving agent and the resolving procedure suitable for a certain compound and the selection and the resolving methods should be made on the trial-and-error basis. ("Kagaku Sousetsu" No. 6, Separation of optical isomers, p. 8, "Nippon Kagakukai", 1989) Under these circumstances, there has been a demand for a new process for producing 2-halo-1-(substituted phenyl)ethanol of a formula (Ia) and optically active substituted styrene oxide of a formula (Ib) by the diastereomer resolving method which is satisfactory from the standpoint of yields and optical purity. ##STR1## wherein X represents a halogen atom, Y is same or different and represents a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.6 alkyl group, a C.sub.1 -C.sub.6 alkoxy group, a C.sub.1- C.sub.6 haloalkyl group or a C.sub.1 -C.sub.6 haloalkoxy group, n is 0 or an integer of 1 to 3, and * represents an asymmetric carbon atom.
In the above definition of substituent groups in the formula (Ia) and (Ib), the halogen atom includes chlorine, bromine, fluorine, and iodine atoms, and the C.sub.1 -C.sub.6 alkyl group includes straight chain or branched alkyl groups having 1-6 carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, and n-hexyl groups. The C.sub.1 -C.sub.6 alkoxy group includes straight chain or branched alkoxy groups such as a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, an n-butoxy group, an n-pentyloxy group and an n-hexyloxy group. The C.sub.1 -C.sub.6 haloalkyl group includes straight chain or branched haloalkyl groups such as trifluoromethyl group. The C.sub.1 -C.sub.6 haloalkoxy group includes straight chain and branched haloalkoxy groups such as difluoromethoxy group.